Curved Space Telescope: E-sail concept to the solar gravitational lens focal region

This paper proposes a Curved Space Telescope (CST) mission concept: using an E-sail propelled spacecraft to reach the solar gravitational lens focal region (SGLFR), and thanks to its properties being able to directly imaging exoplanets. Gravitational lens is the name given to the fact that the curvature of space-time around celestial bodies makes light rays passing nearby change their course. An incoming image concentrated by a gravitational lens is projected onto a region in space, called the focal region. In the case of the Solar Gravitational Lens (SGL) the effect starts at ≈ 550 AU, with easier observing opportunities starting at ≈ 650 AU as the image is clearly separated from the Solar corona and the noise is reduced. The E-sail is a propellant-less propulsion technology, that is suitable for missions requiring long acceleration phases for interplanetary spacecraft. It works by deploying charged metallic tethers into the solar wind, repelling its charged particles and extracting a small thrust in return. The thrust decays with ≈ r - 1 , making the E-sail particularly efficient at large distances from the Sun when compared with a photonic solar sail. When a distance from the Sun is reached where E-sail acceleration and power generation from solar panels become minuscule, both systems are jettisoned for operational simplicity. This article proposes a mission concept based around the E-Sail to propel a spacecraft to the SGLFR. The design proposed in this paper consists on 80 tethers of 26 km charged up to 25 kV, and the trajectory analysis predicts a final radial velocity of 55 km/s and a travel time of 64.21 years towards the target region. The scientific payload consists of a 1-m telescope with coronagraph. The electrical power is generated using solar panels during the acceleration phase, and with a Radioisotope Power System (RPS) setup during coasting, that allows for small trajectory corrections, communications with Earth, and science operations. The communications system consists on a laser emitter directed straight to Earth. The trajectory corrections are performed by field emission electric propulsion (FEEP) thrusters. The total mass is 660 kg. Compared with other mission concepts, the E-sail allows us to bring a larger mass to SGLFR and hence minimises the constrains placed on other systems.